A conventional cell structure for a fuel cell stack is disclosed in Patent Document 1 titled as Fuel Cell Stack Structure. In the fuel cell stack structure disclosed in Patent Document 1, each cell (unit cell) is formed by sandwiching a membrane electrode assembly (MEA) between a pair of separators. The membrane electrode assembly includes a hard resin frame that sandwiches an electrolyte membrane in the periphery. The resin frame part serves as a non-power generating area. In the fuel cell stack structure, the cells are stacked to form a plurality of multi-cell modules. The plurality of multi-cell modules are arranged in series in the cell stacking direction, and the interface between the plurality of multi-cell modules is sealed by a bead gasket.